6-Year Study of Seniors. Neighborhood Environments, Physical Activity & Function Built environment changes have been recommended by the IOM, CDC, and others to improve physical activity (PA). Such changes may be most important for vulnerable groups like older adults who are least active and least studied. Scientists consistently call for prospective studies of built environment and PA. The proposed study is a 6-year follow-up of the Senior Neighborhood Quality of Life Study (SNQLS) cohort of 66+ year-old residents of neighborhoods selected to maximize variability in walk ability and income. Analyses of current data show neighborhood environments are related to PA and BMI. SNQLS is more methodologically advanced than other studies, with objective and perceived measures of both environments and PA, and a prospective follow-up can strengthen evidence of causality. A key innovation is re-assessment of the full range of PA-related environmental characteristics, including walk ability (GIS measured mixed use & street connectivity), microscale features (systematically observed and self-reported streetscape details such as sidewalk quality, safety of street crossings), and access to senior-relevant recreation facilities (GIS and reported). In addition to repeating accelerometer measures, we will add GPS assessment of mobility within neighborhoods. Aim 1, guided by ecological models, is to explain patterns of change in PA from 7-day accelerometry over 6 years by comprehensive measures of neighborhood environments and psychosocial variables. Secondary aims will assess moderators (eg, physical function) of the relationship of 6-year change in PA with environmental measures and environmental correlates of 6-year changes in a validated measure of physical function, walking for transport and recreation, BMI, and sedentary time. Exploratory aims will assess the impact of changing residences and examine correlates of GPS-measured mobility and its health consequences. Based on pilot data, we expect to measure 70% (projected follow-up N=603) of the sample who participated at Time 1. The study will fill many gaps in knowledge about the relation of environments to multiple health outcomes in seniors. The interdisciplinary team will use results to advance the science of environments and health and develop evidence-based guidelines for designing neighborhoods that support healthy aging.